Scroll-type compressors are frequently used in automotive air conditioning systems to compress a recirculated flow of refrigerant fluid and move the fluid through a cooling circuit. The scroll compressor includes two involute or spiral wrapping scrolls. One of the scrolls is fixed in the compressor housing, whereas the other scroll is disposed for orbital movement relative to the fixed scroll for intaking low pressure fluid and discharging high pressure fluid. A rotary drive means extends outwardly from a forward end of the compressor for operative connection to a power take-off of the automotive engine. The drive means extends internally of the scroll compressor and terminates in a drive pin that extends axially off the drive means yet is radially offset, or eccentric, relative to the central rotation axis of the drive means. The end of the drive pin is received in an eccentric bore of a bushing, which, in turn, is centrally and rotatably disposed on the forward face of the orbital scroll. Therefore, as the drive means rotates in the housing, the drive pin forces the orbital scroll to orbit in a small circular path against the fixed scroll.
For smooth and proper operation of the compressor, the bushing must not be permitted to shift axially on the drive pin, otherwise the bushing will not fully engage the drive bearing of the orbital scroll and abnormal or excessive bearing wear will result. Additionally, the bushing and/or an adjacent counterbalancing counterweight may contact the drive pin during operation and result in objectionable noise or wear.
In order to axially retain the bushing on the drive pin, the prior art teaches to form an annular shoulder on the drive pin by reducing its diameter to form a shoulder against which one side of the bushing abuts to prevent relative axial movement in one direction. To prevent relative axial movement in the other direction, a C-type clip seated in an annular groove at the end of the drive pin abuts the opposite side of the bushing. Therefore, the bushing is sandwiched between the shoulder and the C-type clip. The primary deficiency of this prior art arrangement is that the strength of the drive pin is diminished by reducing its diameter to form the shoulder, and additional machining is required to form the shoulder. However, if the shoulder is not formed, the bushing will be permitted to shift axially forward on the drive pin, and thus result in partial engagement of the bushing and objectionable noise and wear, as described above. Also, the shoulder of the prior art drive pin acts as a stress concentrator thereby decreasing the rigidity of the drive pin. Further, the reduced diameter of the prior art drive pin caused by the formation of the shoulder results in a smaller bearing surface for the bushing, which has the undesirable effect of increasing the unit carrying load.